Electronic devices, such as wireless telephones, personal digital assistants, audio/video devices, etc. include integrated circuits (IC) chips or product chips that provide functionality. A product chip may be bound to a printed circuit board or substrate which connects the product chip to other product chips and/or to system components (e.g., processors, memory, etc) of the device.
In certain situations, the device may experience a current spike. Such a current spike may be either induced, for example as part of a certification test, or experienced during use of a product, such as an electrostatic discharge (ESD) received by the device. Current spikes can be received through one of various electrical (i.e., conductive) inputs or input points that are exposed by the device. Examples of exposed input points, include power connectors, data connectors (i.e., connections to other devices), and user input points (e.g., keypads).
Following the fundamental equation of voltage=L di/dt, where L is inductance (i.e., magnetic flux) and di/dt is change of current over time, if a current spike is experienced, a proportionally large voltage spike is also experienced. Example values that may be seen include a 30 Amp current spike that translates to about an 8 kV voltage spike. Such current and associated voltage spikes can cause significant damage to the device.
In order to address problems presented by current spikes, a separate electrostatic discharge or ESD chip is provided with or configured to product chip. The ESD chip is designed to protect the product chip from any such current spikes, typically receiving and diverting (i.e., shunting) the current spike input away from the IC or product chip. The use of a separate ESD chip adds to the size of the device. For example, as new functionality and product chips are integrated into a device, the separate ESD chip or chips take up valuable real estate in the device. Therefore, as devices, such as smart phones, evolve and provide greater functionality, it becomes a challenge to reduce or maintain the size of devices, while introducing new and different product chips and ESD chips.